If your B12 is on the low-normal side, it can't hurt to try supplementing it more. My doctor told me that there's very little risk of toxicity from getting too much B12, so there's no downside to increasing it. Honestly, I felt very much like you describe when my B12 was low: out of it, depressed, angry, tired, weak, confused. I say give it a try. And don't be discouraged if you don't see a change right away. As I said above, it can take a while for the symptoms to go away (I'm still working through my last symptoms).